giúp mình với ạ mình cần gấp c) 2x(x-5)=(x-5)^2 d)92x-1)^2=($-3x)^2 e)2x(3-4x)-5x^2(4x-3)=0 f)(x+8)(x^2-1)=0 g)x^2-5x=6

0 bình luận về “giúp mình với ạ mình cần gấp c) 2x(x-5)=(x-5)^2 d)92x-1)^2=($-3x)^2 e)2x(3-4x)-5x^2(4x-3)=0 f)(x+8)(x^2-1)=0 g)x^2-5x=6”

1. Đáp án + Giải thích các bước giải:

   `c) 2x(x – 5) = (x – 5)^2 ` $\\$ `=> 2x(x – 5) = (x – 5)(x – 5) ` $\\$ `=> 2x(x – 5) – (x – 5)(x – 5) = 0` $\\$ `=> (x – 5)[2x – (x – 5)] = 0` $\\$ `=> (x – 5)(2x – x + 5) = 0` $\\$ `=> (x – 5)(x + 5) = 0 => `\(\left[ \begin{array}{l}x=5\\x=-5\end{array} \right.\) 

   Câu d đề lỗi

   e) `2x(3 – 4x) – 5x^2(4x – 3) = 0 => -2x(4x – 3) – 5x^2(4x – 3) = 0` $\\$ `=> (4x – 3)(-2x – 5x^2) = 0 => (4x – 3).(-x)(2 + 5x) = 0 ` $\\$ `+) 4x – 3 = 0 => 4x = 3 => x = 3/4` $\\$ `+) -x = 0 => x = 0` $\\$ `+) 2 + 5x = 0 => 5x = -2 => x = -2/5`

   f) `(x + 8)(x^2 – 1) = 0 => (x + 8)(x – 1)(x + 1) = 0`

   +) x + 8 = 0 => x = -8

   +) x – 1 = 0 => x = 1

   +) x + 1 = 0 => x = -1

   `g) x^2 – 5x = 6 => x^2 – 5x – 6 = 0 ` $\\$ `=> x^2 + x – 6x – 6 = 0 => x(x + 1) – (6x + 6) = 0` $\\$ `=> x(x + 1) – 6(x + 1) = 0` $\\$ `=> (x + 1)(x – 6) = 0` $\\$ `=>` \(\left[ \begin{array}{l}x=-1\\x=6\end{array} \right.\)

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